Materials having an amorphous structure are known to exhibit high corrosion resistance. Nanocrystalline materials (materials having a grain size below 100 nanometers) are known to be very hard but typically brittle. Microcrystalline materials (materials with grain size below 1000 nanometers) are known to have intermediate corrosion and mechanical properties between amorphous and nanocrystalline materials, but have higher thermal stability than metastable nanocrystalline and amorphous phases.
Research in the fields of nanostructured and amorphous materials has focused on synthesis and processing of bulk amorphous and nanocrystalline alloys. A number of international conferences conduct special sessions directed to these materials including bulk metallic glasses, bulk nanocrystalline materials, ultrafine grained materials, and nanostructured coatings. These materials are generally developed at request of militaries and other industries, but most of the work is still in the research stage.
A development challenge is that nanocrystalline amorphous materials with the most technologically attractive properties have melting temperatures above 1700° F., for example, W, Fe, Ni, Co, Cr and other metal-based alloys. It is a technical challenge to obtain nanocrystalline amorphous structure in materials with such high melting temperature. It can be done if the alloy is solidified from molten phase with very high rate, e.g., above about 100,000 Kelvin degree per second (>105 K/s), but this results in the very thin films/foils (below 1-2 mils thick). Such thin layers without bonding to a part surface are useless for practical application.
Numerous industries require materials and coatings with enhanced wear and corrosion resistance for severe environments. Thermal spray coating processes are leading technologies for obtaining high quality coatings in terms of high adhesion to the substrate, density, and homogeneity. The coatings/materials that combine high corrosion resistance and enhanced mechanical properties such as hardness and wear resistance can solve significant technical and economical problems in metallurgy, paper industry, medicine, oil transportation and other fields.
There continues to be a need in the art to provide improved materials and coatings with enhanced wear and corrosion resistance for severe environments such as for landing gears, airframes, ball valves, gate valves (gates and seats), pot rolls, work rolls for paper processing, and the like.